1. Field of the Invention
The present invention relates to a rotation angle detecting unit which detects a rotation angle of an accelerator pedal.
2. Description of Related Art
Conventionally, an accelerator opening used for operation control of an engine or the like is detected as a rotation angle of an accelerator pedal (hereinafter referred to as a pedal) rotated by pedal force and is outputted to an electronic control unit (ECU). A rotation angle detecting unit, which detects the rotation angle of the pedal, includes a movable part, which is attached to a pedal arm (hereinafter referred to as an arm) and is displaced according to rotation of the pedal, and a stator, which outputs an electrical signal according to the rotation angle of the pedal due to a magnetic or electric interaction with the movable part.
For example, as shown in FIG. 3, a rotation angle detecting unit 100 in JP2004-108214A includes a shaft member 103, which is firmly fixed to an arm 101 and is rotated with the arm 101, and which is supported by a predetermined bearing part 102, the movable part 104, which is a permanent magnet attached to the shaft member 103, and a stator 105, which is a hole IC that senses a magnetic variation according to rotation of the permanent magnet and converts the variation into an electrical signal to be outputted.
The rotation angle detecting unit 100 includes a pedal rotor (hereinafter referred to as a rotor) 107, which engages the arm 101 and is urged and rotated in a direction opposite to pedal force by a predetermined restoration spring 106, and a hysteresis plate 108, which slidingly contacts the rotor 107 and applies frictional force to the rotor 107 in a direction opposite to a rotational direction of the rotor 107. The rotation angle detecting unit 100 generates pedal force hysteresis using a difference of a direction, in which the frictional force is applied to the rotor 107 by the hysteresis plate 108, between when the pedal force is strengthened and when the pedal force is weakened. Additionally, the pedal (not shown) is formed integrally with the arm 101 at an end portion of the arm 101 on the side opposite to an end portion of the arm 101, which the rotor 107 engages.
Since a direction in which the pedal force is applied to the pedal varies widely, the movable part 104 itself also sways in the various directions and accordingly the electrical signal outputted from the stator 105 is not stabilized in the rotation angle detecting unit 100, in which the movable part 104 is integrated with the pedal and the arm 101.
Furthermore, when the movable part 104 is integrated with the pedal and the arm 101, the arm 101 and the movable part 104 are rotated simultaneously with the application of the pedal force to the pedal. Accordingly, the electrical signal outputted from the stator 105 accords promptly with the rotation of the pedal. As a result, throttle opening control in the ECU or the like needs to be deliberately delayed in order to obtain a sense of delay in an engine blow as in a conventional throttle-by-wire accelerator device.
A rotation angle detecting unit including a pedal, which is rotated and urged in a direction opposite to pedal force directly by a restoration spring, and a movable part, which is displaced according to the rotation of the pedal, is disclosed in EP1273989A1 and EP1388455A1. However, according to the above rotation angle detecting unit, the movable part easily sways due to rattling of the restoration spring and accordingly an electrical signal outputted from the stator is not stabilized because the movable part is attached near an end portion of the restoration spring.